1. Field of the Invention
The present invention relates to an apparatus for generating contour signal data of a desired image region of an original such as a photograph and to a method and apparatus for producing a cut-out mask based on the generated data. More specifically, it relates to a method and apparatus for generating image contour data for producing a cut-out mask used in recording a reproduction image only of the desired image region.
2. Description of the Prior Art
In photoprocessing, a specified image region of an original is extracted to be reproduced in the following manner. First, the contour of the image region is displayed and a mask is prepared in which either the exterior or the interior of the contour is made transparent and the other is made opaque. This film is called a "cut-out mask". This mask is superimposed in registration with the original. Thereafter, it is exposed as it is. Consequently, a reproduction is obtained in which only the desired image region is extracted.
A method for generating an image contour for easily producing the above mentioned cut-out mask is disclosed in U.S. Pat. No. 4,441,020 entitled "Method for Tracing an Object" issued on Apr. 3, 1984 and assigned to the assignee of this invention. However, the above mentioned method has a disadvantage that errors occasionally occur in reading data for producing the cut-out mask.
In view of the foregoing, an improved method for producing the cut-out mask eliminating the above described disadvantage was proposed. This is disclosed in U.S. Pat. No. 4,561,061 entitled "Method of Tracing/Recording Image Lines and Apparatus Therefore" issued on Dec. 24, 1985 and assigned to the assignee of the present invention. FIG. 1 is a block diagram showing the structure of the contour tracing/recording apparatus disclosed therein. The conventional image contour data generating apparatus comprises a coordinate reader 213 for inputting approximate outline data, a table 214 for reading the actual contour data by an image sensor 209, a CPU 212 for the image data processing, and so on.
In the conventional image contour data generating apparatus, first, approximate outline positions of the original are inputted by the coordinate reader 213 to be stored in the memory 219 through the CPU 212. Thereafter, the original is moved to the table 214. The table 214 is moved based on the inputted data of the memory 219 and the accurate contour data is read by the image sensor 209.
However, this improved method for generating image contour still has the following disadvantages. One of the disadvantages is that reading errors can not be completely eliminated since the precision of the data reading image sensor is not good. The other disadvantage is that data reading takes long time since the data reading operation is carried out in two steps. Namely, in the reading of the contour data, the reading of the approximate outline data is carried out by the coordinate reader and the detection of the accurate outline should be carried out on the separate table. A further and most significant disadvantage is that the original film, the approximate data of which is read, must be moved from the coordinate reader to the reading table for the image sensor in generating the image contour. Consequently, reading errors grow larger.